We plan to resolve the isozymes of housefly acetylcholinesterase, and if possible determine the oligomeric basis for their isozyme character. Purification of the enzyme from resistant and susceptible strains will be attempted in order to determine the molecular basis of the alteration in acetylcholinesterase. Our newly developed techniques for measuring (separately) the binding and phosphorylation constants governing the reaction between organophosphates and acetylcholinesterase will be explored with a number of new organophosphates. Fluorescent correlation spectroscopy will be used to study the effects of DDT upon real and artificial membranes. Purification of acetylcholine receptor from houseflies will be attempted, and antibody techniques will be explored to examine the relation between this and the vertebrate acetylcholine receptors.